+
+ /// provideInitialHead - when constructing an ilist, provide a starting
+ /// value for its Head
+ /// @return null node to indicate that it needs to be allocated later
+ static NodeTy *provideInitialHead() { return 0; }
+
+ /// ensureHead - make sure that Head is either already
+ /// initialized or assigned a fresh sentinel
+ /// @return the sentinel
+ static NodeTy *ensureHead(NodeTy *&Head) {
+ if (!Head) {
+ Head = ilist_traits<NodeTy>::createSentinel();
+ ilist_traits<NodeTy>::noteHead(Head, Head);
+ ilist_traits<NodeTy>::setNext(Head, 0);
+ return Head;
+ }
+ return ilist_traits<NodeTy>::getPrev(Head);
+ }
+
+ /// noteHead - stash the sentinel into its default location
+ static void noteHead(NodeTy *NewHead, NodeTy *Sentinel) {
+ ilist_traits<NodeTy>::setPrev(NewHead, Sentinel);
+ }